Numerous different particulate detection and free water detection systems are currently available and are used in laboratories and other locations for determining the contaminate levels in various fluids. One important application is in testing of aircraft and jet fuel for assuring the fuel is within acceptable levels of contaminants. The aircraft or jet fuel must typically be tested for determining whether particulates are below an acceptable value and whether free water in the fuel is below an acceptable value.
Testing of particulate levels has typically been accomplished by obtaining a given volume of the fuel i.e., 700 ml milliliters and forcing the sample fuel through a pair of filter elements of 0.8 micron porosity. The filter elements are placed back to back so that, as the fuel is forced therethrough, the first filter element captures substantially all particulates. However, both of the filter elements are equally exposed to the fuel or other fluid coloration features and, thus, both filter elements obtain the same tint or color dependent on the fuel or fluid coloration. Thereafter, individual opacity readings are taken of the respective filters and the differential between these readings is used as a representative measure of particulate level independent of fuel coloration.
Free water contamination is normally detected by using a single filter element or impregnated with fluorescence which reacts with free water to proportionally fluoresce in the presence of ultraviolet light. Accordingly, the sample fuel i.e., 450 milliliters is passed through the impregnated filter element thereby exposing and allowing any free water to come in contact with the filter element. The filter element is then placed adjacent a ultraviolet light source whereby visible light is emitted and a reading is taken from a photocell such as a photoresistor. The photocell reading is proportionally representative of the free water volume in the fuel convertible to a measure of free water per given fuel volume.
The foregoing method of measuring particulate and free water in fuel and other fluids is known and described in, for example, U.S. Pat. No. 4,044,604 and U.S. Pat. No. 4,200,064 both of which are assigned to the assignee of the present invention. In fact, U.S. Pat. No. 5,200,064 discloses an apparatus through which the readings obtained are readable on a display. Unfortunately, that and prior apparatus require substantial operator intervention, for example, zeroing and calibrating the readings, knowing when to take the readings and converting the various readings to meaningful measurements such as parts per million (PPM) for free water content and milligrams per liter for particulate quantities. Unfortunately, this operator required intervention leaves room for potential error and, thus, inaccurate readings.
Accordingly, a need exists for a particulate and free water contamination measuring apparatus requiring substantially no operator intervention except placement of the free water and particulate test sample filter elements or pads for reading purposes and which therefrom directly displays, in human understandable form, such as for the particulate contamination level in milligrams per liter and the free water contamination in parts per million.